If emigration had been included in the Olympics when they were first introduced, Ireland would be a great sporting nation. Nonetheless the scale of the emigration is sometimes slightly exaggerated.
I have seen it stated online that “Four out of every five children born in Ireland between 1931 and 1941 emigrated in the 1950s.” (For example, here and here.) This is not true.
The claim first appears on p.379 of JJ Lee (1989) Ireland, 1921-1985: Politics and Society. This is an excellent book, but the claim is slightly incorrect. Lee attributes the claim to Tobin (1984:156) The Best of Decades. I tracked this book down on eBay. Tobin in turn was citing Garret FitzGerald, who wrote in the Irish Times in September 1966 that “[Current low unemployment] contrasts sharply with the position between 1954 and 1961 when net emigration averaged over 45,000 a year, or the equivalent of 80 per cent of those born eighteen or twenty years earlier.”
FitzGerald notes that the emigration rate is “the equivalent” of 80% of those born twenty years earlier. This definition could include, for example, two thirty year-olds and their three small children. In that respect the original 80% statistic is stated too strongly: restricting emigration exclusively to those born between 1931 and 1941 invalidates the claim. We know that many of the emigrants of the 1950s were young children.
In summary, the statement that four out of every five children born in Ireland between 1931 and 1941 emigrated in the 1950s is incorrect. What is true is that around 57,000 were born each year in the 1930s, and around 45,000 people (i.e. about 80% of 57,000) emigrated each year in the 1950s. The starkness of that statistic doesn’t require any exaggeration.